The connective tissue of lung, which is composed of fibrous structures and carbohydrate protein macromolecules, is of fundamental importance in maintaining both normal structure and mechanical and functional properties of the lung. Although much information is available on the fibrous proteins of lung's connective tissue, very little is known of proteoglycans. This research program is studying the nature of proteoglycans from different tissue sites of the lung and exploring the potential of proteoglycans in biologic functions. Preliminary observations noted the isolation of different proteoglycans from gas-exchange and pleural tissues. Their different compositions suggest that the function of proteoglycans might vary in each of these tissue areas. Earlier studies on glycosaminoglycans also suggested this. Further characterizations of individual proteoglycans are being performed. As a model of human disease, experimental emphysema in rabbits will be studied. The primary aim of the research program is to define precisely the chemistry and function of proteoglycans in normal lung and the role proteoglycans play in the development of chronic lung diseases.